Silicon wafers are used as the substrate to build the majority of semiconductor devices. Manufacturing of silicon wafers starts with growth of single crystal silicon ingots. A sequence of processes is used to turn a silicon ingot into wafers. A wafer can be a complete wafer or a sliced silicon (substrate) wafer. The process typically consists of the following steps: slicing, edge profiling or chamfering, flattening (lapping or grinding), etching, and polishing. Grinding is a flattening process for the surface of silicon wafers, not for the edges.
On the front side of a wafer, semiconductor devices are built. The back side of a wafer is typically thinned to a certain thickness by grinding. Such grinding the back of the wafer is simply called backside grinding, usually done by a diamond wheel. In backside grinding, the removal amount is typically a few hundred microns (in wafer thickness), and it is typically carried out in two steps: coarse grinding and fine grinding.
Coarse grinding employs a coarse grinding diamond wheel with larger diamond abrasives to remove the majority of the total removal amount required, as well as a faster feed rate to achieve higher throughput. For fine grinding, a slower feed rate and a fine grinding wheel with smaller diamond abrasives are used to remove a small amount of silicon.
A conventional grinding tool typically has multiple grinding modules, which are used to grind the backside of a semiconductor wafer 1 in various stages of the grinding process. Coarse grinding is done with a first grinding wheel at a first stage or station, and fine grinding is subsequently done with a second grinding wheel at a second stage. Movement between the two different stages or stations causes delay and misalignment issues that can impact the cost and quality of the overall process.
The drawings, schematics and diagrams are illustrative and not intended to be limiting, but are examples of embodiments of the invention, are simplified for explanatory purposes, and are not drawn to scale.